Process and device for charging into a smelting unit

ABSTRACT

A process and a device for charging a primary product for pig iron into a smelting unit are provided. According to the process and device, some of the primary product that has been formed by reducing oxidic iron carriers is stored in the hot state in a reservoir tank before being supplied into the storage device or charging device that is directly connected to the smelting unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.13/502,282, filed Jul. 25, 2012, which is a national phase conversion ofPCT/EP2010/064867, filed Oct. 6, 2010, which claims priority of AustrianApplication No. A1636/2009, filed Oct. 16, 2009, the contents of whichare incorporated herein by reference. The PCT International Applicationwas published in the German language.

TECHNICAL FIELD

The present disclosure relates to a process and to a device for charginga primary product for pig iron into a smelting unit.

BACKGROUND

In certain reduction processes for finely particulate iron ore, forexample the FINEX.® process, direct reduced iron (DRI) is produced influidized-bed reactors by means of a reducing gas. This direct reducediron has a degree of reduction of about 50-95%, depending on theoperational method, and is finely particulate in common with the ironore used. For complete reduction and to produce pig iron, the directreduced iron DRI is supplied, after a compacting step in which so-calledhot compacted iron (HCI) is obtained, to a storage device or chargingdevice, through which a reducing gas possibly flows, and from there to asmelting unit, for example a melter gasifier. A storage device, alsocalled an HCI bin, or charging device fulfills, inter alia, a bufferfunction for ensuring that hot compacted iron is charged continuouslyinto the smelting unit. Furthermore, it makes it possible to preheatmaterials which are additionally to be charged into the smelting unit,for example pellets or lump ore or coke, by the reducing gas. In thiscase, the storage device is arranged above the smelting unit in order tomake charging from the storage device into the smelting unit in thedirection of the force of gravity possible.

During normal operation of a FINEX.®. installation, after the compactingthe predominant part of the hot compacted iron obtained in thecompacting step is supplied directly in the hot state to the storagedevice or charging device.

During normal operation of a FINEX.®. installation, after the compactinganother part of the hot compacted iron obtained in the compacting stepis utilized in order to provide a reservoir of compacted iron storedoutside the storage device or charging device. This reservoir ofcompacted iron is typically required, for example, during the start-upor shut-down of a FINEX.®. installation. In conventional systems, thehot compacted iron which is not conveyed directly into the storagedevice is typically cooled very quickly in a quench tank with water andthen stored in the open under atmospheric conditions. As soon as thiscooled, stored compacted iron may be required for addition into thesmelting unit, it is supplied to the storage device or charging device.It is preheated in the latter before being charged into the smeltingunit.

It may be disadvantageous in this case that the compacted iron cooled inquench tanks tends toward reoxidation upon storage, and that a highinput of energy is required to preheat said compacted iron before it ischarged into the smelting unit. The time required for preheating thematerial may additionally increase the duration of the start-up process.Furthermore, the operation of the quenching apparatuses is often complexand necessitates time-consuming and expensive handling and disposal ofcold briquetted iron and slurry. The installation parts involved mayrequire costly maintenance and operation.

The same conditions also apply of course if, instead of a FINEX.®.process with HCI as the primary product, use is made of a process inwhich hot briquetted iron (HBI) is produced as the—briquetted, i.e.compacted—primary product from oxidic iron carriers.

In the case of non-compacted primary products, too, for example lowreduced iron (LRI), it is accordingly disadvantageous not to store theprimary product in the hot state.

SUMMARY

In one embodiment, a process is provided for producing pig iron in asmelting unit from a primary product which has been obtained by reducingoxidic iron carriers by means of a first reducing gas, wherein theprimary product is supplied to a storage device or charging device whichis directly connected to the smelting unit and from which addition intothe smelting unit takes place, wherein some of the primary product isstored in the hot state in a reservoir tank before being supplied intothe storage device or charging device which is directly connected to thesmelting unit.

In a further embodiment, the oxidic iron carriers are finely particulateiron ore. In a further embodiment, the oxidic iron carriers are lump oreor pellets. In a further embodiment, the primary product is hotcompacted iron HCI. In a further embodiment, the primary product is hotbriquetted iron HBI. In a further embodiment, the primary product is hotlow reduced iron LRI. In a further embodiment, a reoxidation protectivegas which inhibits reoxidation of the primary product is flushed aroundthe primary product stored in the hot state in the reservoir tank. In afurther embodiment, a second reducing gas flows through the storagedevice or charging device which is directly connected to the smeltingunit. In a further embodiment, the first reducing gas and the secondreducing gas originate from the same source. In a further embodiment,the addition from the storage device or charging device into thesmelting unit takes place substantially according to the force ofgravity.

In another embodiment, a device is provided for carrying out any of theprocesses discussed above, comprising at least one reduction unit forreducing oxidic iron carriers by means of a first reducing gas, a firstreducing gas line which issues into the reduction unit, a smelting unitfor producing pig iron from the primary product which has been obtainedduring the reduction of oxidic iron carriers by means of the firstreducing gas, and a supply device for supplying primary product into astorage device or charging device which is connected to the smeltingunit via at least one addition line, wherein the addition line issuesinto the smelting unit by way of an addition opening, and wherein afeeding device for feeding primary product to the supply device ispresent, wherein a reservoir tank for storing primary product in the hotstate is present, as too is an introduction device for introducingprimary product into the reservoir tank, wherein the reservoir tank isalso connected to the supply device.

In a further embodiment, a compacting device for compaction and/orbriquetting is present, wherein the compacting device is located betweenthe reduction unit and the supply device and between the reduction unitand the introduction device. In a further embodiment, a feeding devicefor feeding compacted and/or briquetted primary product from thecompacting device to the supply device is present, and in that thereservoir tank is connected to the compacting device via an introductiondevice for introducing compacted and/or briquetted primary product fromthe compacting device into the reservoir tank 14. The device as claimedin either of claims 11 and 12, wherein a second reducing gas line issuesinto the storage device or charging device.

In a further embodiment, the first reducing gas line and the secondreducing gas line are connected to a unit for producing reducing gas,wherein the first reducing gas line and the second reducing gas line areconnected to the same unit for producing reducing gas. In a furtherembodiment, a reoxidation protective gas line for supplying reoxidationprotective gas issues into the reservoir tank. In a further embodiment,the reservoir tank is arranged at a lower height than the additionopening into the smelting unit. In a further embodiment, the smeltingunit is a melter gasifier. In a further embodiment, the reduction unitis a fixed-bed reactor or a fluidized-bed reactor.

BRIEF DESCRIPTION OF THE DRAWINGS

Example embodiments will be explained in more detail below withreference to figures, in which:

FIG. 1 shows a schematic structure of a device according to an exampleembodiment with fluidized-bed reactors.

FIG. 2 shows a schematic structure of a device according to an exampleembodiment with a fixed-bed reactor.

DETAILED DESCRIPTION

Some embodiments disclosed herein provide a process and a device forproducing pig iron from a primary product in which said disadvantagesare avoided.

For example, one embodiment provides a process for producing pig iron ina smelting unit from a primary product which has been obtained byreducing oxidic iron carriers by means of a first reducing gas, whereinthe primary product is supplied to a storage device or charging devicewhich is directly connected to the smelting unit and from which additioninto the smelting unit takes place, characterized in that some of theprimary product is stored in the hot state in a reservoir tank beforebeing supplied into the storage device or charging device which isdirectly connected to the smelting unit.

The oxidic iron carriers are converted into a primary product forproducing pig iron, for example direct reduced iron DRI, by reduction bymeans of a first reducing gas. If the product of the reduction is notlumpy, but rather finely particulate, the manageability can be improvedby subjecting it to compaction by means of compacting devices, whichcomprise compacting machines and crusher systems. Some of the primaryproduct is stored in a reservoir tank before being supplied into astorage device or charging device which is directly connected to thesmelting unit for producing pig iron.

In this case, the iron primary product is not cooled by quenching, butinstead is stored in the hot state in the reservoir tank. If compactiontakes place, the primary product is stored in the reservoir tank aftercompaction has been effected.

In this way, no time-consuming preheating of this material is necessaryin the event of charging into the smelting unit. The primary productstored in the reservoir tank can be added into the storage device orcharging device during a start-up process. This can also be effectedduring normal operation, in order to compensate for fluctuations inquantity during the production of the primary product by the addition ofprimary product to the storage device or charging device.

The storage device and charging device are to be considered equivalent,since both devices are suitable for receiving delivered primary productbefore addition into the smelting unit, or before addition into thesmelting unit delivered material lingers for a period of time in acharging device before it enters into the smelting unit, since passagethrough the charging device requires a certain amount of time. Duringthis time, the material is therefore located in the charging device andis thus stored therein.

According to different embodiments of the process, the oxidic ironcarriers are finely particulate iron ore, or they are lump ore orpellets.

According to one embodiment of the process, the primary product is hotcompacted iron. Reference is typically made, for example, to hotcompacted iron HCI if the density of the primary product is lessthan/equal to 4.5 kg/dm.sup.3, and the metallization is <88%. HCIpossibly contains additions.

According to one embodiment of the process, the primary product is hotbriquetted iron HBI. Reference is typically made, for example, to hotbriquetted iron if the density of the primary product is greaterthan/equal to 5 kg/dm.sup.3, and the metallization thereof is greaterthan/equal to 88%. HBI typically contains no additions.

According to one embodiment of the process, the primary product is hotlow reduced iron.

It may be preferable for a reoxidation protective gas which inhibitsreoxidation of the primary product to be flushed around the primaryproduct stored in the hot state in the reservoir tank. It may thereby bepossible to prevent reoxidation, in the worst case marked as a fire,during storage in the reservoir tank. A suitable reoxidation protectivegas is, for example, an inert gas such as nitrogen or a reducinggas—this reducing gas may be for example the first reducing gas or thesecond reducing gas, which is also introduced hereinbelow.

Accordingly, the risk to safety when carrying out the process accordingto certain embodiments is reduced compared to conventional systems. Thenon-oxidizing, i.e., for example inert or reducing, atmosphere withinthe reservoir tank prevents the reoxidation of the primary product andreduces the negative effects on the smelting unit as a result of the useof primary product with a low or greatly fluctuating degree ofreduction.

According to one embodiment of the process, a second reducing gas flowsthrough the storage device or charging device which is directlyconnected to the smelting unit.

According to a particular embodiment, the first reducing gas and thesecond reducing gas originate from the same source, for example thesmelting unit, i.e. a melter gasifier. In this way, the number ofinstallations required for providing reducing gases may be reduced.

It may be preferable for the addition from the storage device orcharging device into the smelting unit to take place substantiallyaccording to the force of gravity. The expenditure in terms of apparatusand energy for conveying the primary product from the storage device orcharging device into the melter gasifier is thereby kept small. Inprinciple, however, the addition can also be effected counter to theforce of gravity, i.e., for example in such a manner that the storagedevice or charging device is located beneath an opening for the additionof primary product into the smelting unit, and the primary product hasto be conveyed from there upward, i.e. counter to the force of gravity,to the addition opening. Similarly, the addition opening and the storagedevice or charging device can be located to the side of one another atone height, in which case the primary product has to be conveyed out ofthe storage device or charging device sideways to the addition opening,i.e., not in the direction of the force of gravity. More energy and moreexpenditure in terms of apparatus are required for sideways or upwardconveying than for an addition which is effected substantially accordingto the force of gravity, i.e., downward. In this case, the term“substantially” means that, in addition to a downward movement, theaddition may also involve a sideways movement of the added material, forexample if the opening from which the primary product leaves the storagedevice or charging device does not lie vertically above the additionopening through which it is added into the smelting unit.

Some embodiments further relate to a device for carrying out any of theprocesses disclose herein, which device may include at least onereduction unit for reducing oxidic iron carriers by means of a firstreducing gas, a first reducing gas line which issues into the reductionunit, a smelting unit for producing pig iron from the primary productwhich has been obtained during the reduction of oxidic iron carriers bymeans of the first reducing gas, and a supply device for supplyingprimary product into a storage device or charging device which isconnected to the smelting unit via at least one addition line, whereinthe addition line issues into the smelting unit by way of an additionopening, and wherein a feeding device for feeding primary product to thesupply device is present, characterized in that a reservoir tank forstoring primary product in the hot state is present, as too is anintroduction device for introducing primary product into the reservoirtank, wherein the reservoir tank is also connected to the supply device.

The oxidic iron carriers are reduced by means of a first reducing gas inat least one reduction unit, which for example can be in the form of afluidized-bed reactor or a fixed-bed reduction shaft. The first reducinggas used for reduction is supplied by means of a first reducing gas linewhich issues into the reduction unit.

The addition line, which issues into the smelting unit by way of anaddition opening, may also be part of the charging device.

The reduction unit can be, for example, a fixed-bed reactor or afluidized-bed reactor.

The primary product which has been obtained during the reduction ofoxidic iron carriers and is possibly compacted or briquetted is fed to asupply device for supplying primary product by means of a feedingdevice. The feeding device may be, for example, a chute, a screwconveyor, a conveyor channel or a pipe. By means of the supply devicefor supplying primary product, for example a hot conveyor, the primaryproduct is transported into a storage device or charging device.

The storage device or charging device is connected to the smelting unitvia an addition line, through which primary product from the storagedevice or charging device is added directly into the smelting unit. Itgoes without saying that additional devices can be present in theaddition line, for example valves or lock devices. The addition lineissues into the smelting unit by way of an addition opening, throughwhich material originating from the storage device enters the smeltingunit.

Furthermore, the device according to certain embodiments has a reservoirtank for storing primary product in the hot state.

Said reservoir tank is connected both to an introduction device forintroducing primary product into the reservoir tank and to the supplydevice. The introduction device is, for example, a down pipe, a chute, ahot conveyor, a screw conveyor or a star feeder. Primary product cantherefore be introduced into the reservoir tank and fed from thereservoir tank—for example via a screw conveyor, a star feeder, anintermediate hot conveyor, a valve, a pipe or a chute—to the supplydevice.

The reservoir tank is lined with refractory material. The storagecapacity thereof should advantageously cover the demand for primaryproduct, for example hot compacted iron HCI, for operation of the devicefor about 12-24 hours to about two days for carrying out the processaccording to certain embodiments. By way of example, a demand for 4600 tHCI would correspond to a reservoir tank volume of about 2.times.900m.sup.3.

According to one embodiment, a compacting device for compaction and/orbriquetting is present, wherein the compacting device is located betweenthe reduction unit and the supply device and between the reduction unitand the introduction device. In this case, the compacting device isconnected in each case to the two device parts between which it islocated. In this context, “between” is to be understood in respect ofthe flow of material from the reduction unit to the smelting unit. Thematerial taken from the reduction unit, for example DRI, is compacted inthe compacting device, which comprises compacting machines and crushersystems. In this case, hot compacted iron HCI or hot briquetted iron HBIis formed, for example, as the primary product.

In this case, it may be preferable for a feeding device for feedingcompacted and/or briquetted primary product from the compacting deviceto the supply device to be present, and for the reservoir tank to beconnected to the compacting device via an introduction device forintroducing compacted and/or briquetted primary product from thecompacting device into the reservoir tank.

According to one embodiment, a second reducing gas line issues into thestorage device or charging device. By coming into contact with thesecond reducing gas which is fed in through this reducing gas line,material located in the storage device or charging device is possiblypartially reduced or heated. In this case, the first reducing gas lineand the second reducing gas line are connected to a unit for producingreducing gas, where according to one embodiment the first reducing gasline and the second reducing gas line are connected to the same unit forproducing reducing gas. A unit for producing reducing gas is to beconsidered a source for reducing gas.

It may be preferable for a reoxidation protective gas line for supplyingreoxidation protective gas to issue into the reservoir tank. The hotprimary product, for example hot compacted iron HCI, located in thereservoir tank can thereby be protected against reoxidation.

According to one embodiment, the reservoir tank is arranged at a lowerheight, for example level with the ground, than the addition openinginto the smelting unit. This leads to savings in production material andsteel structures when constructing the reservoir tank or whenconstructing supporting structures for the reservoir tank.

According to one embodiment, the smelting unit is a melter gasifier. Itcan also be a blast furnace.

Compared to the quenching of primary product, for example HCI, beforestorage, as carried out according to conventional systems, certainembodiments of the invention have the advantage that no wet quenchedprimary product, for example HCI, is mixed with hot primary product, forexample HCI, thereby reducing the risk of explosion as a result of theformation of hydrogen. Furthermore, the design according to certainembodiments may eliminate the need to acquire and operate a quench tankfor cooling primary product. The amount of process water required cantherefore be reduced.

A further advantage of certain embodiments is that a storage device orcharging device, for example an HCI bin, can have a smaller design,since material for compensating for fluctuations in the production ofprimary product does not have to be present in the HCI bin, but insteadcan be taken from the reservoir tank. The expenditure for materials andwork for the construction of the HCI bin and also the overall heightthereof may therefore be reduced.

It may be preferable for at least two reservoir tanks to be present sothat it is possible to use a redundant tank during maintenance work.

Primary product from the reservoir tank can also be supplied to aplurality of different smelting units, for example a melter gasifier anda blast furnace.

Referring to the example system of FIG. 1, finely particulate iron ore 1is introduced into a cascade of fluidized-bed reactors 2 a, 2 b, 2 c. Afirst reducing gas is introduced via the first reducing gas line 3 intothe fluidized-bed reactor 2 c, after leaving the latter is guided via aconnection line 4 into the fluidized-bed reactor 2 b, after leaving thelatter is guided via a connection line 5 into the fluidized-bed reactor2 a, and is removed from the latter via a top gas line 6. The firstreducing gas line 3 emanates from the melter gasifier 7, in which pigiron is produced from hot compacted iron. Product taken from thefluidized-bed reactor 2 c is compacted to form hot compacted iron bymeans of a compacting device, which comprises an intermediate tank 8, acompacting machine 9 a and a crusher system 9 b. The hot compacted ironis supplied to a storage device 11, the HCI bin, via a supply device 10.The HCI bin is arranged above the melter gasifier 7. The storage device11 is connected to the melter gasifier 7 via an addition line 12, viawhich hot compacted iron HCI is added from the storage device 11 intothe melter gasifier 7 according to the force of gravity. The additionline 12 issues into the melter gasifier 7 by way of an addition opening13. A second reducing gas line 14, emanating from the melter gasifier 7,issues into the storage device 11.

Hot compacted iron is directly fed from the crusher system 9 b by meansof a feeding device, which is represented in the figure by means of aline 16 proceeding from a chute 15. If the chute 15 is set accordingly,hot compacted iron produced in the compacting device can be introduceddirectly into the reservoir tank 19 via an introduction device, which isrepresented by a line 17 and a hot conveyor 18. The inert gas nitrogenis conducted into the reservoir tank 19 via a reoxidation protective gasline 20 which issues into the reservoir tank 19. The reservoir tank 19is connected to the supply device 10 via the reservoir outlet line 21and the hot conveyor 22. Therefore, hot compacted iron can be taken fromthe reservoir tank 19 and supplied to the storage device 11 as required.

In FIG. 2, device parts corresponding to those in FIG. 1 are providedwith the same reference symbols as in FIG. 1.

FIG. 2 differs from FIG. 1 in that, instead of fluidized-bed reactors,use is made of a fixed-bed reactor 24 as the reduction unit. Lump oreand pellets are introduced as oxidic iron carriers 23 into saidfixed-bed reactor. The fixed-bed reactor is connected to the firstreducing gas line 3, through which first reducing gas flows in. Consumedreducing gas is removed via the top gas line 6. Primary product issupplied from the fixed-bed reactor 24 either via the line 16 to thesupply device 10 or via the line 17 to the hot conveyor 18, via whichthe hot primary product is conveyed into the reservoir tank 19. Primaryproduct can be supplied from the reservoir tank 19 via the export line25 to a blast furnace 26.

LIST OF ELEMENTS REFERENCED IN THE DRAWINGS

1 Finely particulate iron ore

2 a, 2 b, 2 c Fluidized-bed reactors

3 First reducing gas line

4 Connection line

5 Connection line

6 Top gas line

7 Melter gasifier

8 Intermediate tank

9 a Compacting machine

9 b Crusher system

10 Supply device

11 Storage device

12 Addition line

13 Addition opening

14 Second reducing gas line

15 Chute

16 Line

17 Line

18 Hot conveyor

19 Reservoir tank

20 Reoxidation protective gas line

21 Reservoir outlet line

22 Hot conveyor

23 Oxidic iron carriers

24 Fixed-bed reactor

25 Export line

26 Blast furnace

What is claimed is:
 1. A process for producing pig iron in a smeltingunit from a primary product which has been obtained by reducing oxidiciron carriers using a first reducing gas, comprising: storing an amountof the primary product in a hot state in a reservoir tank; and supplyingthe primary product, including the amount stored in the hot state in thereservoir tank, to a storage device or charging device which is directlyconnected to the smelting unit; and adding the primary product from thestorage device or charging device into the smelting unit.
 2. The processof claim 1, wherein the oxidic iron carriers are finely particulate ironore.
 3. The process of claim 1, wherein the oxidic iron carriers arelump ore or pellets.
 4. The process of claim 1, wherein the primaryproduct is hot compacted iron HCI.
 5. The process of claim 1, whereinthe primary product is hot briquetted iron HBI.
 6. The process of claim1, wherein the primary product is hot low reduced iron LRI.
 7. Theprocess of claim 1, further comprising flushing a reoxidation protectivegas which inhibits reoxidation of the primary product around the primaryproduct stored in the hot state in the reservoir tank.
 8. The process ofclaim 1, wherein a second reducing gas flows through the storage deviceor charging device which is directly connected to the smelting unit. 9.The process as claimed in claim 8, wherein the first reducing gas andthe second reducing gas originate from the same source.
 10. The processof claim 1, wherein the addition from the storage device or chargingdevice into the smelting unit takes place substantially according to theforce of gravity.